Characterisation and Interpopulation Variability of a Complex HpaI Satellite DNA of Drosophila seriema (repleta Group)

A HpaI satellite DNA has been isolated and characterised from the genome of Drosophila seriema, a cactus-breeding species endemic to the rock fields of the Espinhaço Range in Brazil. The monomer sequences are slightly A + T rich (66%) and there is a significant variation of repetition length (343–391 bp). The length variability is mainly due to a 22 bp indel in some repeats and the presence of a highly variable region characterised by several DNA rearrangements, including indels, inversions and duplications of small sequence segments. The retarded mobility of monomers observed after gel electrophoresis suggests DNA curvature. Thirty satDNA repeats were analysed in samples from five populations which cover D. seriema geographical distribution. Previous studies showed that these populations present low levels of chromosomal divergence in contrast to high levels of mtDNA divergence. The variability among the 30 repeats is pretty low, on average 2%. The results showed that the satDNA sequences are rather homogeneous on both intra and interpopulational levels, presenting no specific feature(s) that could discriminate a particular population or groups of geographically close populations. Possible factors responsible for such homogeneity are discussed.